Electrical apparatus



June 17, 1952 J. v. cAPU-ro ETAL 2,600,844

ELECTRICAL APPARATUS Filed oct. 16'. 1947 .s sheets-sheet 1 June 17, 1952 J. v. 'cAPUTo ETAL ELECTRICAL APPARATUS Filed 001'.. 16. 1947 5 Sheets-Sheet 2 INVENTORS. V Ca/vv/, c-C ford'.

z-zvzes fianzas BY frown/5K2 June 17, 1952 J. v. cAPUTo ETAL ELECTRICAL APPARATUS 5 Sheets-Sheet 5 Filed Oct. 16. 1947 INVENTORS. t-zmes Cafva.

Y'omds {Crau/fari BY /7' OPA/IKS'.

June 17, 1952 J. v. cAPuTo ETAL 2,600,844

ELECTRICAL APPARATUS Filed oct. 1s, 1947 S Sheets-Sheet 4 INVENTOR A54 Jmes UA1/gua J. V. CAPUTO ET AL June 17, 1952 ELECTRICAL APPARATUS 5 Sheets-Sheet 5 Filed OCC. 16. 1947 J. w. w maf. www M www f VJ@ m ij WM Patented June 17, 1952 ELECTRICAL APPRATUS 'James VsCaputo, Youngstown', Ohimnd Thomas .J. Orawford.;Berk1ey, Mich.; said Crawford as- `signortosaizilCaputo Applicationoctbcr '16, 1947, kSerial No. 780.170

(C1. lib-212) 1.0 :Claims 1 The present Vinvention relates lto vrotating :electrical apparatus 4and more specifically to lan elec trio dynamo which is adapted, 'among-otherzuses, for the supplying of heavy pulses -of ycurren'tzfor relatively short intervals for a spot, projection,

or ash-type electric -resistance welding.

1I-he principal objects of v'the'present invention are: to provide an improved ,electrical current generati-ng apparatus-of the lcharacter described; to provide an improved 'cooling system lfor fsuch apparatus; to provide such a cooling system which will not act to unbalance the rotating parts of Athe apparatus; to providesuch acoo'ling system which will not form gas pockets; to providesuch a ycooling system in which the rotation ofr themoving partsof the electric apparatus will cause the coolant 'to circulate; Vto provide anew and improved energy storage and lconversion apparatus; to provide an improved 'energy/storage dynamoelectric machine having a flywheel for energy storage; to provide -suc'h a' `machine which rotates about a vertical axis; to provide means :for reducing the end thrust against the bearings in such a vertically arranged velectric machine; to provide a ux path 'for'su'ch aivertically arranged machine which includes' iat `least a. portion of the ii'ywheel :whereby the vattractive effect of `the flux will support the flywheel; to provide :an-'improved exciting `control system'ior such an electric machine; to provide Jsuch-aan exciting system in Ywhich the output voltage is relatively independent of changes o'f speed `of rotation ofthe machine; and generally toprovide a new and improved electric"powersgenerating apparatus for use in welding systems.

@ther and more detailed 'objects of theinvention will appear inthe following description and in the appended claims'.

In the accompanying drawings, which illustrate preferred embodiments ofthe invention and throughout the several views of lwhich corresponding'reference characters are used `to designate corresponding parts:

Figure l isa View in elevation-of a motor-gen erator unit embodying the/invention;

vFig. 2 is aview of the lower `portion ofthe homopolar Agenerator shown partly in central vertical section, the sections being taken along various radiallines to best illustrate the various constructional features thereof;

Fig. '3 is a View of the'upper portion of -the generator with certain Vparts shown in radialfs'ection to .illustrate certain constructional features thereof.;

Fig. 4 'is an enlargedview showing, in central vertical section, the coolant connections .therefor;

Fig. l5 is a view l*taken substantially .along :the line 5--5 of Fig. 2';

Fig. y6 `is .a partial view ytaken .substantially along 'the 1line .i6-5.6' of Fig. 12';

Fig. is apartial vieu/taken substantialh/:along the 'line fi--ll of 112;

lFig. '8 vis la partial view taken Isulistantially along the line 8-8.1of yFig.2.;

Fig.-9 is a `schematicelectrical:diagramshowingthey :exciting circuit for the vrhomopolar .motor generator;

Fig. `110 -is a partial view `showing lthe offset relationship yof the rotor inductor :bars

Fig. 111 tis Aa lpartial .sectional Viewfshovving the sealing member for thecollector ring;

Fig. VL2 is anenlarged View of a-collectorbrush; and

Fig. 13 is arschematic view ofafwe1ding .system embodying ithe invention.

It will vhe appreciated :from .a ,complete understanding :of the :present `invention 'that .fthe aimprovements` `thereof may `loe y.embodied V:in apparatus of `.widely varying capacities and .intended for widely different :types of service .that incertain of. their broaderaspects many features of the present complete system may be utilized independently .of other features y.and that ithe present improvementsxmay .beemhodied inwidely diner-ing structural sforms. :The V.prf-:sent .disV closure, therefore, o1 .a :particularstructuralx embodiment iis Ato `:be regarded` in an .illustrative and not iin alimitingsense.

Referring rst `to Fig. .1, 1the .motor ,generator combination il' fcomp'rises a homopolar ,generator portion A2 a motor Adriving portion f4, .and :an-.exciter 6 arranged inconcentric fashion sone :atome the 'other in a single casing and themotors `,of which are :all secured '.togetherzupon a common shaft i8. Thesingle casing 4for the '.motorgenerator uniticomprises va series .of casing :sections lli, t2, ylil, :and I6 which are V-suitalzoly holtedtogether as bymeans of bolts 1&8.

tThe -homopolar generator L2 `'comprises essentially` 4two `complementary fsimilarhalves, one ,of which is V.housed :within vthe casing ilu Aand the otherof which is housed within the .casing f2 ingenerallythesame manneriasis disclosed-:and claimed `in J. V. f'Caputo `Patent No. f25(i05;6Q9`, dated June 1'8, 41985.

In -the present construction -a laminated score 20 is providedv on the shaft :8 'for frotation v`.therewith and' isfaligned with'` a flaminated .'field,- struc 'ture '22 '-held Vrigid with theflower :casing `section i8. In the said Caputo patent, flux flows longitudinally of the rotating shaft through a series of laminated core structures arranged longitudinally of the shaft; however, in the present application, flux flows directly into the shaft and longitudinally therethrough to the lower end portion, some of the flux returning to the lower casing section i8 across an air gap 24 into an annular platelike portion 26 of the section ID and then upwardly through legs 28 of the casing section t8 back to the laminated held structure 22 and across an air gap 38 back to the laminated core 20. Other of the flux passing downwardly longitudinally through the shaft 8 flows outwardly through a flywheel 32 which is keyed by means of key 34 to the lower end of the shaft 8 through an air gap 36 to the annular platelike portion 23 and then returns to the laminated core in the manner above described in connection with the flux which passes across the air gap 24.

By properly proportioning the length of the air gaps 24 and 33, the flux made to pass across the gap 3G may be proportioned so that substantially the entire weight of the flywheel 32 may be supported due to the attractive effect of the flux passing across the gap 36. If desired, the gaps 3S and 24 may be so proportioned that not only the weight of the flywheel 32 is supported by flux passing across the gap 36 but also the weight of the other parts carried by the shaft 8 so that the end thrust during operation of the motor generator l may be relieved from the lower bearing 38 thereof. The lower bearing 38 for the shaft section Bb is preferably carried by a lower end bell 48 of the casing section l0 which is secured thereto as by stud screws 42. Bolts 44 may extend through other apertures in the bell 48 whereby the motor generator l may be secured to a suitable footing 46. The end bell 48 is preferably made of nonmagnetic material such as stainless steel or aluminum bronze and is electri cally insulated from the bearing 33 by suitable insulation 4l. Similarly an upper end bell 48 of nonmagnetic material carries an upper bearing 58 for the shaft section 8c, the bearing 50 being electrically insulated from the bell 49 by insulation 4'1.

The upper portion of the homopolar generator 2 located within the casing section i2 is similar to that described and comprises a laminated core 28a, a laminated field structure 22a separated by an air gap 38a so that flux from the structure 22a may flow across the gap 38a through the laminated core 26d upwardly through the shaft 8 radially outwardly across an air gap 24al and back to the laminated eld structure 22a through the casing section i2. The laminated cores 28 and 28a are provided with laminated inductors 48 which are spaced circumferentially around the laminated cores 2G and 28a and extend substantially parallel to the longitudinal axis of the rotating common shaft 8. As shown in said Caputo patent, the portion of the inductors 48 located in the core 28 are preferably slightly circumferentially offset from the portion of the inductors 48 carried by the laminated core 20a to provide a diagonal connecting portion to permit limited longitudinal expansion and contraction of the inductors 4S. The ends of the inductors 48 are each connected to radial flanges 52, 52a of collector rings 54, 54a respectively. The rings 54 and 54a are located concentric of the shaft 8 and held for rotation therewith between wedge-shaped collars 56. Annular insulating members 58 (shown in detail in Fig. 11) insulate the collector ring 54 from the wedge-shaped collars 56 whereby the ring 54 is electrically insulated from the shaft 8 and spaced therefrom to provide an annular chamber 5l. The collector ring 54 is located 1ongitudinally along the shaft intermediate the core 2D and the annular platelike portion 26 while the ring 54a is similarly placed above the core 20a and below an upper horizontal magnetic platelike member 62. Suitable field windings 60 are provided on the upper surface of the annular portion 26 for inducing a flow of iiux across the air gaps 24, 30, and 35 in a path as above described.

The laminated field structures 22 and 22a each are provided with longitudinally extending conductor busses 64 which are parallel with the inductors 48 and are preferably equally spaced around the structures 22 and 22a. The sets of conductor busses carried by the field structures 22 and 22a, unlike the inductors 48, are not interconnected together. All of the conductor busses 64 associated with the field structure 22 are electrically connected to an annular conducting ring 86 which serves as one output terminal of the homopolar generator 2. The conductor busses 64 associated with the field structure 22a are likewise all connected together to an annular conducing ring 68 which serves as the other output terminal of the homopolar generator 2. The rings 66 and 68 are closely adjacent one another but are insulated from one another by an annular insulating ring 10. The outwardly extending end portions of all of the conductor busses 64 overlie the collector rings 54 and 54a, depending upon whether the busses are associated with the field structure 22 or 22a. To each of these overlying portions of the busses 64 is secured a brush holder 12 carrying one or more brushes 74 which are resiliently urged against the associated collector rings 54 or 54a. Each of the brushes 14 is electrically connected with the brush holder 12 by means of a pigtail '16.

As is clearly shown in Fig. '7, the brushes 14 are held by the holders 12 in sets which extend at an angle relative to the radial lines of the co1- lector rings and are arranged in pairs extending at equal acute opposite angles with respect to the radius lines. In this manner the current flowing through the brushes does not have any effect in the flux field of the generator. In some instances, however, it may be desirable to increase or decrease the flux upon increase in delivered current, and in such instances one or more groups of brushes may be arranged at; equal acute angles so that either the additive or subtractive effect will be produced, since under these conditions the effect of the various sets located at one angle is not neutralized by the effect of an equal number of corresponding sets arranged at the same angle but in opposite directions from the radius line.

The common shaft 8 of the motor generator i comprises a section 8a which is magnetic in character having secured thereto as by bolts a lower end section 8b of nonmagnetic material and an upper end section 8c also of nonmagnetic material. The sections 8b and 8c may, for example, be aluminum bronze or stainless steel. The section 8c extends upwardly beyond the upper end bell 62 through the driving motor 4 and through the exciter 6 and terminates externally of the top of the common casing of the motor generator i. The rotating member of the driving motor 4 is suitably secured to the shaft section 8c, so that when the driving motor 4 is energized lit will rotate the common shaft 8l, causing rotation of the rotating portions of the homo'polar generator 2 and will also cause rotation of the rotor of the exciter 6. Preferably a three-phase alternating current motor is employed; however, any other type motor, whether alternating current or direct current, may be utilized. The exciter 5 may be any of the direct current generator types of proper rating whereby a direct current voltage across its output terminals will be produced in accordance with its speed of rotation and the degree of energization of its exciting winding as will be more thoroughly brought out hereinafter.

Referring more specifically to Figs. 2 and 4,

the common Vshaft 8 has a longitudinal central aperture or vpassageway 18 extending substantially the Alength of the shaft and a plurality of radially extending passageways leading from the aperture 18 to annular chambers 51 formed between the outer peripheral surface of the shaft 8 `and the inner peripheral surface of the colflector ring 54and bound at its top and bottom by the wedge collars 56. One set of radial passageways 82 extends from the aperture 18 radially outwardly and opens into the annular chamber 51 adjacent the lower one of the wedge collars 56. Preferably more than one of these lower radial passageways 82 are provided, and when such a plurality are used, the radial passageways are spaced around the shaft 8 in such a manner that the static balance of the shaft 8 is preserved. A second set of these radial passageways 82 extends through the wall of the shaft from the aperture 18 thereof to the top portion of the annular chamber 51 adjacent the top one of the wedge collars 55. This top set of radial passageways 82 preferably comprises more than one passageway arranged about the shaft 8 in ra manner similar to the arrangement of the lower set of radialpassageways 82. Similar passageways interconnect the aperture 18 of the shaft 8 with a similaiannular chamber intermediate shaft 8 and the 'collector ring 54a located within the` upper casing section l2.

An Lashaped fitting 90 isl provided for the open upper end of the shaft 8 and is suitably secured to this upper end ofthe shaft 8 ina rotative uidtype manner by means of packing 92 held by a cannut 94. The L-shaped fitting,r 90 is anchored tofthecasing of the motor generator I by suitable means whereby it is held against rotation with the shaft 8 and in a substantially fixed longitudinal position adjacent the open upper end of ther-shaft. VA suitable fitting S6 connects the hollow interior of the L-shaped tting 90 to a drain cond-uit Y9,8 which conducts the coolant to a suitable drain-or radiating surface if the coolant is to bere-used. The L-shaped fitting 80 has an aperture |00 ythrough one wall thereof, which aperture |00 is arranged concentrically with the passageway 18 of the shaft 8. A coolant inflow tube |02 extends 'through this 'aperture |50 and conc'entrically downwardly 'through the passageway 18 'of "the shaft 8 and terminates slightly upwardly fromthe lower portion of the lower end ofthe passageway 10. A suitable cap nut |04 and 'packing |55 seal Ythe tube |02. within the aperture |00 to the L-shaped fitting 90 whereby coolantfflowthrough the aperture along the outside of thetube |02 is prevented. Coolant from afsuitablesource -of supply is conducted to the tube |02'throug`h suitable means, not shown, but which willbe well understood by those skilled in the'art; down throughlthef'tube |02 into-the lower 6 end of the passageway 18 from whence it flows upwardly within the passageway 18 around the tube |92 and outwardly through the conduit '98. As the shaft 8 rotates, the coolant within the lower set of radial passageways 82 tends to flow outwardly from the passageway 18 with a force depending on the 'density of the coolant and thel speed of 'rotation of the shaft 8. Likewise, the coolant within the upper set of radial passage-A ways 82 will also tend to ow outwardlyV therek through from the passageway 18 of the :shaft 8 upon rotation thereof, depending on vthe speed of rotation of the shaft 8 and the density of the coolant Tin this upper set of radial passageways 82. If the density of the coolant in both of the sets of 'radial passageways 02 is exactly the same, they will exert a substantially equal and opposite force upon the coolant in the annular chamber 5-1, and no circulation of coolant from the passageway 13 of the shaft 8 through the annular chamber 51 will result. However, since during normal operation of the homopolar generator 2 heat will be developed in vthe collector rings 54, the coolant within the annular chamber 51 will tend to be heated thereby. The `higher the temperature of the coolant the less dense it becomes; and since with increase in temperature it tends to expand upwardly and increase the temperature of the coolant in the upper set of radial passageways 82, the pressure in the two sets of passageways 82 unb'alances and a flow of coolant is Apro'- vided from the passageway 18 of the shaft 8 through the lower sets of radial passageways 82, upwardly through the annular chamber 51 and back again lto the passageway 18 'of the shaft 8. The rate of flow 'of coolant will be generally proportional to the temperature of the collector rings 54. Therefore, as the output of the homopolar generator goes up and the temperature of the ring 54 tends to increase, the rate of flow of coolant through the annular chamber 51 will increase, maintaining the temperature of the collector ring within a safe limit. Conversely, as the output of vthe homopolar generator 2 decreases, the heating effect on the collector ring 54 will be reduced and the rate of coolant flow through the annular chamber 51 will decrease so that an excessive amount of coolant is not used to excessively reduce the temperature of the collector ring 54 below a normal temperature operating range. The collector ring 54a, is `similarly cooled by the beforementioned sets of 'passageways 82 associated therewith in a manner which it is believed will be evident from the description of the cooling of the collector ring 54.v

terminals connected directly across the output terminals |50 and |82 of the auto transformer |50. A transformer |64 has the terminals of its primary winding 55 connected across the output terminals |60 and |62 of the auto transformer |50. The output terminals of the auto transformer |58 are connected across lthe alternating current input terminals of a full-wave bridge-V typerectlfier |88 having its direct-currentoutput terminals connected directly across the exciting winding |56 of the exciter 6.

The secondary winding of the transformer |64 is connected across the alternating current input terminals of a full-wave bridge-type rectifier which has its direct current output terminals arranged in series circuit with the output terminals of the exciter 6 and the field windings 08 of the homopolar generator 2. The Voltage of the exciter 6 is arranged to be less than the voltage of the rectifier' |10. rlhe polarity of the output terminals of the exciter 6 and the directcurrent output terminals of the full-wave rectifier |14 are preferably arranged in bucking relation so that the curent flow through the field winding 60 will be proportional to the differential in voltage between that generated by the exciter 6 and that appearing across the direct-current output terminals of the full-wave bridge-type rectifier |18. It will now be evident that the voltage generated by the homopolar generator 2 will be a resultant of the rotational speed of the shaft 8 and of the diierential in voltage between that generated by the exciter- 6 and that appearing across the output terminals of the rectifier As the speed of rotation of the shaft 8 falls, the voltage generated by the exciter 8 will be reduced, thereby permitting a greater flow of current through the field winding 60 of the homopolar generator 2; and if the voltage characteristics of the exciter 6 with relation to speed of rotation of the shaft 8 are properly proportioned, this increase in excitation of the eld winding 68 of the homopolar generator 2 due to the decreased terminal voltage of the exciter 6 will be sufhcient so that the output voltage of the homopolar generator appearing between the conductor rings 66 and 68 will be substantially constant within any normal variable speed range of rotation of the shaft 8.

It is believed that the remaining details of construction may best be understood by reference to a description of operation of the motor generator which is as follows:

Upon energization of the motor 4 by suitable means well known in the art and notl shown herein for simplicity, the shaft 3 will be rotated at motor speed. Upon energization of the auto transformer |58 the excitingwinding |56 of the exciter 6 will be energized through the auto transformer |58 and the rectifier |68 whereby a voltage will appeal' across the output terminals of the exciter 6. At the saine time, a unidirectional Voltage will appear across the output voltage terminals of the bridge rectifier |10, which voltage is preferably balanced with respect to the normal output voltage oi the exciter 6 so that it is enough greater than the output voltage of the exciter 6 to cause normal exciting current to ow through the field windings E8 of the homopolar generator 2. With the eld windings 80 excited, flux will flow through the paths in the generator hereinbefore described and across the air gaps 24, 88, and and similar air gaps 24a and 38a of the upper portion of the homopolar generator 2. This iiux passes substantially radially across the gaps 38 and 38a and through the laminated cores 28 and 28a downwardly and upwardly through the shaft section 8a. It should be noted that since the end bells 48 and 49 and shaft sections 8b and 8c are of nonrnagnetic material and will not conduct flux, the iiux path will not extend through the bearings 38 and 50. Since the bearings 38 and 58 are completely insulated from the end bells 48 and 49 no current will pass therethrough due to any possible unbalance in voltage induced due to the cutting of the ux by the shaft section 8a.

As the shaft section 6a and the cores 20 and 20a rotate, this iiux will be cut by the inductors 88, causing a voltage to be induced therein. Since the direction of cutting of the flux by the inductors 48 associated with the core 20 and the inductors 48 associated with the core 20a is in the same direction, the voltages induced by the cutting of the flux passing across the gaps 30 and 38a will be additive. The upper collecting ring 54a will be of one polarity and the lower collector ring 54 will be of the opposite polarity. The collector rings are electrically connected by means of the associated brushes 14 to the respective sets of conductor busses 64 and therethrough to the conducting rings 66 and 68 which form the output terminals of the homopolar generator 2. The rings 66 and 68 may be connected by suitable conductors |12, |14 connected to welding electrodes diagrammatically shown at |16 and |16 between which the work W ls clamped. A contactor of a type available on the open market is connected in series with the conductor |12. A three-way valve |82 has its inlet conected to a suitable source of fluid pressure through conduit |84 and its outlet connected by a conduit |96 to the pressure chamber |88 of the valve |80. Energization of the control winding |90 of the valve |80 acts to connect the source of fluid pressure to the chamber |88 whereby the associated piston |92 will move downwardly, causing the cam |94 thereof to rotate the bell cranks |96 (one only being shown) whereby the carbon disks |99 and 200 are held in intimate contact for closing the circuit through the conductor |12.

Operation of the valve |82 is preferably controlled by any of the usual contactor controllers 202 which may be purchased on the open market. Such controllers, upon being actuated, will energize the circuit for the winding |90 for a predetermined time interval usually for a limited number of cycles of a sixty-cycle current source after which the winding |90 will be deenergized. Upon de-energization of the winding |90 the valve |82 will close the connection between conduits |84 and |86 and place conduit |88 in open communication with the exhaust conduit 204 whereby fluid pressure is relieved from the chamber |88 at a controlled rate as determined by a control valve 206 located in the conduit 284. As the fiuid pressure escapes from the chamber |88 the piston will move upwardly allowing the bell cranks |96 to rotate clockwise and reduce the pressure at which the disk |98 engages the disk 200, thereby increasing the resistance to current flow therebetween and reducing the current flow through the conductor i12 to a value which preferably does not exceed 5% cf the normal current flow during welding and in many instances to a value considerably below 5%. Continued reduction in pressure permits further clockwise rotation of the cranks |96, and the springs 208, one only of which is shown. will separate the disks |98 and 280 to interrupt the welding circuit through the conductor |12. By so arranging the contacter, current in the order of upwards of 100,000 amperes may be interrupted rapidly without destructive arcing between the disks |98 and 288, since the inductively stored energy of the system will be substantially dissipated before interruption at the disks H13 and 200.

When the contacter 180 controlling the energization of the welding electrodes HG, |18 is closed, whereby welding current is supplied thereto, the power required to effect the welds is somewhat greater than the power which may be transferred by the driving motor 4 to the shaft 8 so that the shaft 8 tends to reduce somewhat in speed. Due to the presence, however, of the fiywheel 32 and the kinetic energy thereof, the shaft B will tend to rotate at a substantially constant speed until such time as energy is absorbed from the flywheel 32 when it slows down somewhat. However, due to the bucking arrangement of the exciting generator, such slow down of the shaft 8 will decrease the bucking voltage applied by the exciter 6 and thereby raisevthe energization of the exciting windings S@ of the homopolar generator 2 so that the voltage output generated by the homopolar generator 2 is maintained substantially constant whereby the potential supplied to the welding electrodes may be held substantially constant and a commercially satisfactory weld be effected between the workpieces W being joined.

As the generator 2 is so used, heat due to the passage of current through the collector rings 54 and 54a will be generated therein, causing coolant to circulate through the annular chambers 51, which ow of coolant through chambers as hereinbefore described will be somewhat proportional to the current output of the generator 2 whereby the rings 5l! and 5ta will be maintained with the normal temperature operating limit. As shown in Fig. l1, the insulating and sealing members 58 comprise a hollow truncated cone portion i12 of mica and a hollow truncated cone portion |14 of silicone rubber. The rubber being more compressible than the mica is initially thicker but, as indicated in Fig. 2, is compressed to the same thickness when a.,- sembled to insure a fluid-tight seal. The rubber |14 in Fig. ll is shown in its expanded condition. When it is compressed, it will expand lengthwise to some extent, and a recess Il@ is provided in the portion |12 for receiving at least some of this displaced rubber, so that when installed with the rubber |14 compressed, the recess |76 will be filled. The portions llt act to positively locate and hold the collector rings 5d with respect to the shaft t, while the rubber H4 seals the joint. If rubber alone were used, the rings 5ft might, under certain conditions of operation, have a vibratory movement with respect to the shaft i3 which might cause unbalance of the rotating parts and jumping of the brushes. When a member 58 of such material is used, the inductor f-B may be soldered in place after assembly of the ring 54 to the shaft ection 8a` The brushes 'M preferably are formed from copper dust with which has been intimately mixed a suitable amount of carbon or graphite dust. A coolant passageway 280 is provided in the upper end portion of the brush M which may be a passageway molded directly in the brush material, one of which is formed directly in the material after the brush is fabricated or one of which is formed by a tube molded in the brush at the time of its fabrication. Lugs are provided on the brushes which t in slots in the brush holder to limit inward movement thereof so that the brush cannot wear away sum.- ciently to expose the passageway 2te.

10 Preferably one or more of the brushes `are formed by the first-named method in which short lengths of tubing 282 and 284 are provided for yconnecting the coolant supply and return to the passageway 280. With this type passageway 280, a certain amount of the collant passes through the brush, similar to oil through a self-oiling bearing, outwardly through the surface of the brush in contact with the ring 54 to aid in providing an oxide film on the ring 54. The use of this type of brush obviates the need for supplying humidity around the contacting brush surfaces to produce the desired oxide film as has often been dene by those skilled in the art by humidifying the atmosphere surrounding brush type dynamoelectric machines. It has been found that this type of cooled brush with the moist surface permits the use of current densities -substantially higher than has heretofore been thought practicable and still maintain a satisfactory brush life.

A brush containing substantially of 300 mesh copper and 10% of 300 mesh graphite compacted and sintered to a density of from 90 to of the density of the basic materials and used with water as a coolant at pressure from l t0 10 pounds per square inch will provide enough water at the brush surface to insure a desirable oxide lm on the rotating metallic surface. Also such a brush has been used with current densities of one thousand amperes and above for protracted periods of time without showing any appreciable wear and it is believed that these densities may be increased severalfold.

What is claimed and is desired to be secured by United States Letters Patent is `as follows:

l. In a homopclar generator, a rotor arranged to rotate about a vertical axis, a hollow vertically extending shaft carrying said rotor andproviding a chamber for the upilow of coolant, means providing a container for coolant outwardly of said sha-ft from the hollow interior thereof, vertically spaced passageways in said shaft coinmunicatively connecting said container with the hollow interior of said shaft, and fluid conveying means for supplying coolant to one end portion of the hollow interior of said shaft, the other end portion of said shaft being open for the discharge of coolant therefrom.

2. In a dynamoelectric apparatus, a support, a rotating member carried for rotation on a vertically extending shaft journaled for rotation in said support, said shaft having a longitudinally extending central passageway, means providing a coolant containing pocket in heat-exchange relation with said member, means providing an inlet passageway to said pocket from said central passageway, means providing an outlet passageway from said pocket to said central passageway, said outlet passageway being elevated above said inlet passageway, and fluid conveying means opening into said central passageway below said outlet passageway.

3. In a dynamoelectric apparatus, a support, a rotating member carried for rotation on a vertically extending shaft journaled for rotation in said support, said shaft having a longitudinally extending central passageway, means providing a coolant containing pocket in heat-exchange relation with said member, said shaft having a radially extending inlet passageway to said pocket from said Central passageway and having a radially extending outlet passageway from said pocket to said central passageway, said outlet passageway being elevated above said inlet pas- 1l sageway, and fluid conveying means opening into said central passageway below said outlet passageway.

4. `In a dynamoelectric apparatus, a vertically extending shaft journaled for rotation about its longitudinal axis, a slip ring carried by said shaft and spaced therefrom to form an annular coolant container, said shaft having a central longitudinally extending passageway centrally. of said container and vertically spaced radially extending fluid-flow passageways, said spaced passageways being located adjacent upper and lower portions of said slip ring and connecting said central passageway with said container whereby coolant will flow outwardly from said central passageway through the lower one of said radial passageways and into said annular container and inwardly to said central passageway from said container through the upper one of said radial passageways.

5. In a dynamoelectric apparatus, a vertically extending shaft journaled for rotation about its longitudinal axis, a slip ring carried by said shaft and spaced therefrom to form an annular coolant container, said shaft having a central longitudinally extending passageway centrally of said container and vertically spaced radially extending fluid-flow passageways, connecting said central passageway with said container whereby coolant will flow outwardly from said central passageway through the lower one of said radial passageways and into said annular container and inwardly to said central passageway from said container through the upper one of said radial passageways, and a coolant-conveying conduit extending centrally of said central passageway for supplying coolant thereto below said upper radial passageway.

6. In a dynamoelectric apparatus, a vertically extending shaft journaled for rotation about its longitudinal axis, a slip ring carried by said shaft, and spaced therefrom to form an annular coolant container, said shaft having a central passageway extending longitudinally and centrally of said container and opening through the top wall of said shaft, said shaft having vertically spaced radially extending fluid-flow passageways connecting said central passageway with said container whereby coolant will flow outwardly from said central passageway through the lower one of said radial passageways and into said annular container and inwardly to said central passageway from said container through the upper one of said radial passageways, and a coolant-conveying conduit extending centrally of said central passageway and above said shaft top wall for supplying coolant thereto below said upper radial passageway.

7. In an apparatus of the character described, a hollow shaft, bearing means for supporting said shaft for rotation of said shaft about its longitudinal axis, voltage inducing means carried by and rotatable with said shaft, a Sleeve member carried by and rotatable with said shaft, conductor means connecting said inducing means with said sleeve member, collector brushes having sliding engagement with said sleeve member, fluid flow conveying means for supplying a coolant to the hollow interior of said shaft at one portion thereof, means for exhausting coolant from said interior at a point spaced on the opposite side of said sleeve member from said one portion, said hollow interior being arranged for coolant flow therethrough to cool said shaft, and means including fluid flow passageways through which coolant from said interior may flow to and return from said sleeve member for cooling the engaging surfaces of said sleeve member with said brushes.

8. The combination of claim 7 in which said last-named means comprises coolant chambers located intermediate said shaft and said sleeve member and coolant chambers within said brushes whereby the heat of said surface is extracted in both directions from said surfaces.

9. The combination of claim 8 in which said bearing means supports said shaft with its longitudinal axis extending substantially vertically and in which said passageways are vertically spaced along said shaft for interconnecting the one of said coolant chambers located intermediate said shaft and said sleeve member with the hollow interior of said shaft.

10. In a homopolar generator, a rotor arranged to rotate about a vertical axis. a hollow vertically extending shaft carrying said rotor in heat exchange relation, the hollow interior of said hollow shaft forming a chamber for the upward flow of coolant, a collector cylinder carried concentrically with and by said shaft at each side of said rotor intermediate portions of said collector cylinders being spaced from said shaft to provide 5 coolant containers, each said container being connected to said hollow interior by a pair of vertically spaced passageways, fluid flow conveying means for supplying coolant to a lower portion of said interior, said lower portion being at least as low as the lowermost one of said passageways, and means to permit flow of coolant outwardly of said interior at a portion thereof above the uppermost one of said passageways.

JAMES V. CAPUTO.

THOMAS J CRAWFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 265,782 Edison Oct. 10, 1882 332,427 Parham Dec. l5, 1885 367,470 Thomson Aug. 2, 1887 1,055,963 Zimmerman Mar. 1l, 1913 1,315,766 Feldman Sept. 9, 1919 1,778,640 Maher Oct. 14, 1930 1,784,102 Lincoln Dec. 9, 1930 2,103,931 Berger Dec. 28, 1937 2,293,508 Killam Aug. 18, 1942 2,389,214 Shobert Nov. 20, 1945 FOREIGN PATENTS Number Country Date 421,840 Great Britain Jan. 1, 1935 453,449 France Apr. 3, 1913 

